To what extent do the PANSS and CGI-S overlap?

Background: The Positive and Negative Symptom Scale (PANSS) and Clinical Global Impression (CGI-S) item for severity are used together to measure severity of psychotic illness. PANSS is the "gold standard" measure of efficacy, but it is not always feasible to use, yet the CGI-S requires validation. Objectives: To examine the overlap between PANSS and CGI-S. Methods: The overlap of the PANSS and CGI-S were examined using data from 7 large antipsychotic clinical trials (n = 4287). Results: Regression analysis identified 21% to 60% overlap of the measures depending on the trial and measurement point. The pooled study mean PANSS value corresponding with a CGI-S of 2, 3, and 4 were 67.1 (n = 799), 79.6 (n = 1645), and 92.4 (n = 1056), respectively. A decrease of I on the CGI-S corresponded to a 20% decline on the PANSS. Of the 37 planned comparisons in these studies, there was an agreement between the PANSS and CGI-S on change from baseline to end point on 32 comparisons and on dichotomized change variables (PANSS <=-20% and CGI-S <=-1 point) on 31 comparisons. The differences in the remaining comparisons would not have changed the conclusions of the studies. The positive and disorganized PANSS scales were the most closely related to the CGI-S, followed by hostility and negative scale with almost no association with anxiety/depression. Conclusions: The CGI-S and PANSS are correlated but are not synonymous. Both measures, however, show substantial agreement in detecting change, and the CGI-S shows overlap with the core symptoms of schizophrenia.